bfc

Bit Field Clear

BFC<c> <Rd>, #<lsb>, #<width>

Clears a bitfield in a register.

Pseudocode Operation

width ← msb - lsb + 1
mask ← ((1 << width) - 1) << lsb
Rd ← Rd AND NOT(mask)

Example

BFC r0, #0, #width

Encoding

Binary Layout

cond

31:28

0111110

27:21

msb

20:16

15:12

lsb

11:7

001

6:4

1111

3:0

Format Data Proc

Opcode 0x07C0001F

Extension A32 (Base)

Operands

Rd
Destination general-purpose register
lsb
Start Bit
width
Width

Other forms of bfc

bfc Bit Field Clear (Thumb)

Reference

View in Arm A64 ISA Reference ↗ Arm AArch32 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x07C0001F	BFC{<c>}{<q>} <Rd>, #<lsb>, #<width>		A32		cond \| 0111110 \| msb \| Rd \| lsb \| 001 \| 1111
0xF36F0000	BFC{<c>}{<q>} <Rd>, #<lsb>, #<width>		T32		11110 \| 0 \| 11 \| 01 \| 1 \| 0 \| 1111 \| 0 \| imm3 \| Rd \| imm2 \| 0 \| msb

Description

Bit Field Clear clears any number of adjacent bits at any position in a register, without affecting the other bits in the register.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    R[d]<msbit:lsbit> = Replicate('0', (msbit-lsbit)+1);
    // Other bits of R[d] are unchanged

bfc